netdev - RE: [PATCH v8 net-next 5/5] net: ena: Add PHC documentation

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Message-ID: <a4be818e2a984c899d978130d6707f1f@amazon.com>
Date: Wed, 5 Mar 2025 12:50:11 +0000
From: "Arinzon, David" <darinzon@...zon.com>
To: Andrew Lunn <andrew@...n.ch>
CC: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Eric Dumazet
	<edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>, Richard Cochran <richardcochran@...il.com>, "Woodhouse,
 David" <dwmw@...zon.co.uk>, "Machulsky, Zorik" <zorik@...zon.com>,
	"Matushevsky, Alexander" <matua@...zon.com>, "Bshara, Saeed"
	<saeedb@...zon.com>, "Wilson, Matt" <msw@...zon.com>, "Liguori, Anthony"
	<aliguori@...zon.com>, "Bshara, Nafea" <nafea@...zon.com>, "Schmeilin,
 Evgeny" <evgenys@...zon.com>, "Belgazal, Netanel" <netanel@...zon.com>,
	"Saidi, Ali" <alisaidi@...zon.com>, "Herrenschmidt, Benjamin"
	<benh@...zon.com>, "Kiyanovski, Arthur" <akiyano@...zon.com>, "Dagan, Noam"
	<ndagan@...zon.com>, "Bernstein, Amit" <amitbern@...zon.com>, "Allen, Neil"
	<shayagr@...zon.com>, "Ostrovsky, Evgeny" <evostrov@...zon.com>, "Tabachnik,
 Ofir" <ofirt@...zon.com>, "Machnikowski, Maciek" <maciek@...hnikowski.net>,
	Rahul Rameshbabu <rrameshbabu@...dia.com>, Gal Pressman <gal@...dia.com>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Subject: RE: [PATCH v8 net-next 5/5] net: ena: Add PHC documentation

> > +The feature is turned off by default, in order to turn the feature
> > +on, please use the following:
> > +
> > +- sysfs (during runtime):
> > +
> > +.. code-block:: shell
> > +
> > +  echo 1 > /sys/bus/pci/devices/<domain:bus:slot.function>/phc_enable
> > +
> > +All available PTP clock sources can be tracked here:
> > +
> > +.. code-block:: shell
> > +
> > +  ls /sys/class/ptp
> > +
> > +PHC support and capabilities can be verified using ethtool:
> > +
> > +.. code-block:: shell
> > +
> > +  ethtool -T <interface>
> > +
> > +**PHC timestamp**
> > +
> > +To retrieve PHC timestamp, use `ptp-userspace-api`_, usage example
> using `testptp`_:
> > +
> > +.. code-block:: shell
> > +
> > +  testptp -d /dev/ptp$(ethtool -T <interface> | awk '/PTP Hardware
> > + Clock:/ {print $NF}') -k 1
> 
> Why is not opening /dev/ptpX sufficient to enable the PHC?
> 
>     Andrew

Hi Andrew,

The reasoning for the enablement option of PHC was explained in patch 3 in the series
https://lore.kernel.org/netdev/20250304190504.3743-4-darinzon@amazon.com/

David